The global usage of polyvinyl chloride (PVC) is second to polyethylene (PE). In 2009, the global production of PVC reached 41,610,000 tons, and the global demand for PVC reached 33,430,000 tons. PVC is not expensive due to its raw material being mass produced by mature process of cracking petroleum. In addition, extensively desired properties of PVC can be easily achieved by incorporation of a variety of additives such as plasticizers. Accordingly, PVC is one of the most used plastic for a wide variety of applications, which is difficultly to be replaced. PVCs classified as soft PVC, semi-hard PVC, and hard PVC depend on the amount of plasticizer within PVC. A soft PVC has a plasticizer amount of 40 phr to 150 phr, a semi-hard PVC has a plasticizer amount of about 15 phr, and a hard PVC has a plasticizer amount of less than 3 phr. PVC products used in many applications for instance include electric wires, electric cables, building materials, car accessories, medical drip bags, package containers, hoses, artificial leathers, and other household products.
Plasticizer is easily released from PVC products into the environment while under high temperature/high humidity conditions, contact with oil, contact with low-polarity organic solvents, or the likes. The issue of the released plasticizers harmful to health should be highly concerned when the PVC product is used in children's toys, food packaging containers, or twist caps of cans. Due to the safety and environmental issues, PVCs are being replaced with a new plastic material, and/or the conventional plasticizers are being replaced with environmentally friendly plastic plasticizers such as non-phthalate type plasticizer, epoxy soy bean oil plasticizers, or triformate plasticizers. Compared to conventional phthalate plasticizers, however, the environmentally friendly plastic plasticizers are not only relatively expensive, but also provide relatively insignificant plasticization effect on PVC. For safety and environmental issues, a novel method of inhibiting the plasticizer released from PVC products is called-for. In recent years, the methods of inhibiting the plasticizer release have been classified into four types: surface coating, crosslinking treatment, barrier layer, and plasticizer modification. However, the surface coating, the crosslinking treatment, and the barrier layer methods may locally vary the properties of PVC products according to a ratio of treatment area to the PVC product size.